Evidence for the weakly coupled electron mechanism in an Anderson-Blount polar metal

Journal Article · 18 July 2019 · Nature Communications

DOI: https://doi.org/10.1038/s41467-019-11172-2 · OSTI ID:1619645

Laurita, N. J.; Ron, A.; Shan, Jun-Yi ; Puggioni, D.; Koocher, N. Z.; Yamaura, K. ; Shi, Y.; Rondinelli, J. M. ; Hsieh, D.

Abstract Over 50 years ago, Anderson and Blount proposed that ferroelectric-like structural phase transitions may occur in metals, despite the expected screening of the Coulomb interactions that often drive polar transitions. Recently, theoretical treatments have suggested that such transitions require the itinerant electrons be decoupled from the soft transverse optical phonons responsible for polar order. However, this decoupled electron mechanism (DEM) has yet to be experimentally observed. Here we utilize ultrafast spectroscopy to uncover evidence of the DEM in LiOsO _3, the first known band metal to undergo a thermally driven polar phase transition ( T _c  ≈ 140 K). We demonstrate that intra-band photo-carriers relax by selectively coupling to only a subset of the phonon spectrum, leaving as much as 60% of the lattice heat capacity decoupled. This decoupled heat capacity is shown to be consistent with a previously undetected and partially displacive TO polar mode, indicating the DEM in LiOsO ₃ .

• Research Organization: California Inst. of Technology (CalTech), Pasadena, CA (United States)
• Sponsoring Organization: USDOE; USDOE Office of Science (SC), Basic Energy Sciences (BES); USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
• Grant/Contract Number: SC0010533; SC0012375
• OSTI ID: 1619645
• Journal Information: Nature Communications, Journal Name: Nature Communications Journal Issue: 1 Vol. 10; ISSN 2041-1723
• Publisher: Nature Publishing GroupCopyright Statement
• Country of Publication: United Kingdom
• Language: English